The present disclosure relates generally to the production of polyolefins and, more specifically, to the reduction and/or prevention of fouling in polyolefin reactors.
This section is intended to introduce the reader to aspects of art that may be related to aspects of the present technique, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
As chemical and petrochemical technologies have advanced, the products of these technologies have become increasingly prevalent in society. In particular, as techniques for bonding simple molecular building blocks into longer chains (or polymers) have advanced, the polymer products, typically in the form of various plastics, have been increasingly incorporated into various everyday items. For example, polyolefin polymers, such as polyethylene, polypropylene, and their copolymers, are used for retail and pharmaceutical packaging, food and beverage packaging (such as juice and soda bottles), household containers (such as pails and boxes), household items (such as appliances, furniture, carpeting, and toys), automobile components, pipes, conduits, and various other consumer and industrial products.
One benefit of polyolefin construction, as may be deduced from the list of uses above, is that it is generally non-reactive with goods or products with which it is in contact as well as with the ambient environment. This property allows polyolefin products to be used in many residential, commercial, and industrial contexts, including food and beverage storage and transportation, consumer electronics, agriculture, shipping, and vehicular construction. The wide variety of residential, commercial and industrial uses for polyolefins has translated into a substantial demand for raw polyolefin which can be extruded, injected, blown or otherwise formed into a final consumable product or component.
The raw polyolefin is typically produced in bulk by petrochemical facilities, which have ready access to monomers, such as ethylene, and comonomers such as alpha olefins (e.g., 1-butene or 1-hexene or 1-octene), that serve as the molecular building blocks of the polyolefins to be produced. The polymerization reaction itself is exothermic, or heat-generating, and is typically performed in closed systems, such as a polymerization reactor, where temperature and pressure can be regulated to produce polyolefins having certain desired properties. In some polymerization processes, the components used for polymerization, such as a monomer, a comonomer, and a catalyst that facilitates the polymerization of the monomer and comonomers, are solvated and/or suspended in a diluent. In these cases, the catalyst and the polyolefin formed as a result of the polymerization are typically suspended in the diluent to form a slurry.
However, in some circumstances the polyolefin reactor may foul, such as when the polymerized product is formed on the reactor walls or when the product cannot be maintained as a slurry. Such a foul may result in a loss in heat transfer, such as due to a reduction in circulation or reduced efficiency at a heat exchanger interface, which may impair or completely negate the capacity to maintain the desired temperature within the reactor. A reactor foul may also result in a reduction in the circulation of the reactor contents and/or in a variation from the desired percent solids (measured by volume or by weight) of the reactor slurry. The weight percent solids (solids wt %) in the reactor may be defined as the ratio of polymer to the total reactor contents. To the extent that a reactor foul may result in deviations from the desired reaction conditions, the polymer product produced during such a reactor foul may not meet the desired specifications; that is, the product may be “off-spec.” In extreme or runaway fouling situations, control of the reaction may be lost entirely, and the reactor may become plugged with polymer, requiring one to three weeks to clear, during which time the reactor may not be operated.